1. Field of the Invention
The present invention relates generally to measuring the electrical characteristics of a material, and more particularly to measuring the resistivity or conductivity of materials which do not possess a defined geometry, such as conductive pastes.
2. State of the Art
Techniques for measuring the conductivity of a material are well known. Conductivity corresponds to the inverse of resistivity, and these two electrical characteristics can easily be correlated to one another.
Typically, the conductivity of a material is measured by contacting two probes (e.g., the probes of a conventional ohmmeter) to opposite ends of the material. A constant electrical current is passed via the two probes through the material. By measuring this current for a given voltage across the two probes, the resistance, and thus the conductivity, of the material can be determined.
The foregoing measurement technique is relatively accurate for detecting conductivity of solid materials having a relatively well defined geometry. However, such a measurement is relatively inaccurate for measuring the conductivity of materials which do not have well defined geometries, such as pastes and other similar materials. Because processes involving paste are common in industries such as the battery industry, conductivity measurements represent an important property of the paste.
Another conventional technique for measuring the conductivity of materials, such as paste, is to use two metal plates for forming a slab of paste therebetween. Conductivity or resistivity can then be measured between the two metal plates. However, this method is also inaccurate because contact between the metal plates and the material is not reproducible.
The inaccuracy of conductivity tests for materials which do not possess well defined geometries is due in part to an inability to establish reproducible contact between the probes and the material. Accordingly, there is a need for an apparatus and method which can accurately detect electrical characteristics of materials which do not possess well defined geometries.